Arrangement for welding, cutting or working materials by means of an electron beam



March 7, 1967 F. SCHLEICH 3,308,263

ARRANGEMENT FOR WELDING, CUTTING OR WORKING MATERIALS BY MEANS OF AN ELECTRON BEAM Filed Feb. 10, 1964 M: 7a-E 661E 3 46L Z v M4 FRITZ SCHLEICH ATTOR N E'Y United States Patent 1 Claim. 61. 219-421 This invention relates to working a material with a beam of charged particles. More particularly to performing operations such as welding, cutting, melting, evaporating, or machining on any material with an electron beam.

It is already known, that one may employ a very intensive electron beam for the purpose of welding two metallic workpieces together, that one may also cut or separate metallic workpieces with an electron beam, and that one may finally also drill or machine work material by means of an electron beam, i.e., that one may work the particular material.

It is also known to produce for this purpose a suitable electron beam focal point by projecting by means of an electron-optical lens a scaled down or reduced picture of a cathode or of a diaphragm through which an electron beam passes.

However, an electron beam produced by such a reduced electron-optical lens is not in all cases appropriate to accomplish directly the objects mentioned above.

Between the electron-optical lens which projects the mentioned reduced picture of the electron source and this picture there exists only an interval of about 4 to 6 cm., otherwise one would obtain unreasonably large dimensions of the electron beam apparatus. In the case of a workpiece which has an exactly level or a substantially level surface, it is possible to place the surface to be worked without diiiiculties into the plane of the above mentioned reduced electron-optical picture. But in the case where the workpiece of which the surface to be worked is, for example, the bottom of a cup and when the cup edge is higher than the mentioned distance of 4 to 6 cm., it is not possible to produce with the above mention-ed reduced lens alone a sharp focal point on the workpiece.

A further difliculty which arises in using the above mentioned beam cross-section obtained by electronoptical reduction resides in the fact that although it is still possible to locate in the small interval between the electron-optical lens and the plane of the reduced picture an electromagnetic deflection system for the movement of the electron beam relative to the workpiece surface only a relatively small surface area may be scanned by the electron beam on the workpiece, which is not sufiicient for all working purposes. It is desirable to adjust the electron beam relative to the surface on the workpiece to be worked also with the mentioned electro-magnetic deflecting device because mechanical movement of the workpiece relative to the stationary electron beam is not in all cases possible with the desired speed, or it provides in many cases a technically inconvenient solution.

The invention relates to an arrangement for welding, for cutting or for working materials by means of an electron beam in which a first electron-optical lens projects a scaled down or reduced picture of an electron beam source and is characterized in that from this reduced picture a non-magnified or a weakly magnified picture is projected through an additional electron optical lens on the workpiece.

By the choice of an appropriate focal distance of the additional electron optical lens one has now a means of providing a sufficiently large interval between the workpiece surface to be treated and the last electronoptical lens.

Experiments have shown that one may work by reducing the image by means of the first electron-optical lens l5-18 times and by magnifying the image by means of the second electron-optical lens about 2.5 times. The space between the main planes of the two lenses can amount to about 13 cm., while having acceptable dimensions for the entire apparatus. This provides a distance of the workpiece from the weakly magnifying electron-optical lens of about 30 cm. This space above the workpiece surface is entirely sufiicient to make possible a working of workpieces having the form of the above mentioned cup, and is also sufiicient to arrange above the workpiece an electromagnetic deflection system which permits the adjustment of the impingement point of the electron beam over a sufiiciently wide area of the workpiece.

On the basis of the diagrammatic drawings an embodiment of the invention is illustrated which simultaneously shows an improvement of the arrangement according to the invention, which may be associated with the deflection system, which is located between the workpiece and the non-magnifying or weakly magnifying electron-optical lens. All the elements of the cathode ray device which are not essential to the invention, such as the adjusting devices for the beam, are not shown in the drawing.

In the drawing numeral 1 designates a cathode, numeral 2 a control cylinder and numeral 3 a grounded anode of cathode ray generating system. In the structure 4a a high voltage of about kv. is produced and fed to a structure So by means of a high voltage cable having a grounded sheath. This structure contains a device 6:: for producing an adjustable heating voltage, a device 7a for producing control pulses and a device So for producing an adjustable biasing voltage for the control cylinder 2. These voltages are fed over a high voltage cable to the beam generating system 1, 2, 3.

The pulse duty factor of the control impulses may be for example 1:2, i.e., the pulse duration and the pulse interruption are equally long. The duration of an individual electron beam impulse is chosen in this case to be about 10- seconds.

Below anode 3 an electron-optical lens is arranged in the housing 4 of the electron beam apparatus. This lens, consisting of a coil 5 fed by direct current, projects a reduced picture of the electron beam source or in the plane of an apertured diaphragm 6. The electron beam source thus may be seen either in the cathode surface or in the central aperture of anode 3 filled with electron rays. This reduced picture in the plane of the apertured diaphragm 6 is now pictured by means of an additional electron-optical lens consisting of a direct current fed coil 7 in the plane of the workpiece 8 to be treated. In view of the distances illustrated in the drawing between the apertured diaphragm 6 and coil 7 on one hand and coil 7 and workpiece 8 on the other hand the size of the electronoptical picture in the plane of the apertured diaphragm 6 and on the surface of the workpiece 8 is approximate ly the same.

It may be seen already in the drawings that due to the ingenious insertion of the lens 7 between the lens 5 and the workpiece, there is now provided a considerably larger free space above the workpiece, while one would have available only a very small free space if one would place the workpiece in the plane of the apertured diaphragm 6. I

According to the arrangement of the invention one is thus able to work also workpieces which would otherwise not find room in the limited space available between the lens 5 and the plane of the apertured diaphragm 6.

The embodiment of the invention illustrated shows also a further improvement which relates to the design of the electromagnetic deflection device located between the lens 7 and the workpiece 8.

It has been mentioned already above that it is not always appropriate or possible to displace the workpiece 8 within the work chamber 9 relative to the stationary electron beam 10. It is basically possible to displace this workpiece 8 which is mounted by means of clamping jaws on a table 12 in two coordinates which are for example perpendicular to each other relative to the stationary electron beam 10, and to guide thus the electron beam in each case exactly on the point of the workpiece to be treated.

In the case where, for example, within a very short time a series of holes are to be made in the workpiece 8, it is appropriate to displace the electron beam 10, after passing lens 7, by means of an electromagnetic deflection device.

A deflection device which constitutes an improvement of the apparatus described is disclosed in its structure and operation hereafter by means of the drawings for the specific case wherein the workpiece 8 in addition to a hole at the point of the dot-and-dash line 13 which may be located for example in the center of the workpiece, another hole is to be provided at the point of the dot-and-dash line 14, and a third hole at the point of the dot-and dash line 15.

The hole 13 may be produced by the electron beam in the center of the workpiece 8 without any ditticulty in the conventional manner. To produce the following hole of the desired series of holes, that is to say the hole at the point of the dot-and-dash line 14, the electron beam 10 is deflected as indicated by dotted line 10a by means of a known deflection device 16 consisting of four coils and thereafter is deflected once more in an additional electromagnetic deflection device 17 consisting also of four coils and located below the deflection device 16, so that it travels again parallel to the direction of the original beam 10. In this manner the drilling produced at the point of the dot-and-dash line 14 it may be produced exactly parallel to the drilling at the point of line 13. The drilling at the point of line 15 may now be produced in that one deflects the beam in the deflection device 16 somewhat more strongly than for producing the drilling 14 and by providing in the deflection device 17 such a current magnitude that at the point of the dot-and-dash line 15 the beam impinges again perpendicularly to the workpiece surface, i.e., parallel the direction of the original beam 10.

A further improvement is obtained from the following consideration.

For each electron-optical picture of a parallel beam in one point, one may designate a quantity Ar which is defined by the equation Ar==C' 'at The quantiy Ar is the radius of the electron optical picture of the parallel beam and the angle a is the so called aperture angle or opening angle, namely the half opening angle of that beam cone whose base line lies in the bore of the electron-optical lens and whose apex lies in the spot of the focal point. The quantity C5 is called the aperture fault constant.

In view of the fact that the requirement of a small focal point necessitates a small value of Ar and the requirement of a large intensity necessitates a large value of a, it is obvious that the aperture fault constant C; must become as small as possible,

It is already known that in the case of electron-optical lenses the magnitude C divided by the so-called working distance, i.e., by the distance between the electron-optical lens and the plane of the sharp optical picture has a minimum value depending on a characteristic lens parameter k For the value It is applicable the relationship:

Wherein C is a constant which is dependent on the relationship of the bore diameter and the slot width of the electron-optical lens, Ni is the number of ampere turns, and U the accelerating voltage of the electrons.

In regard to the present objects the working distance A is based on the above mentioned considerations, and for the additional electron-optical lens provided according to the invention it is recognized that one must work in the minimum point of the mentioned ratio of the aperture fault constant and of the working distance, if one desires to produce a focal point which is suitable for welding, cutting, or working materials, i.e., a focal point which is at the same time small and also very intensive.

What is claimed is:

A device for welding, cutting or working materials by means of a source of a beam of charged particles comprising:

means providing a beam source of charged particles,

21 first electron optical lens located between the source and the material to be worked,

said first lens providing a reduced image of said beam source, a second magnetic electron optical lens located between the first lens and the materials to be worked,

said second lens working with a minimum value of the ratio k, comprising the division of the aperture constant by the working distance and where k is defined by the relationship wherein c is a constant depending on the ratio of the bore diameter and the slot width of the lens, Ni is the number of ampere turns, and U is the acceleration voltage of the electrons.

JOSEPH V. TRUHE, Primary Examiner, 

